1. Field of the Invention
This invention relates generally to lubrication systems, and is concerned in particular with although not limited to rolling mill lubrication systems where a liquid lubricant is applied to multiple components and where some but not all of the thus applied lubricant is susceptible to being contaminated by externally applied cooling water and entrained particulates, e.g., dirt, mill scale, etc.
2. Description of the Prior Art
In a conventional rolling mill lubrication system, for example that employed with a high speed finishing block of the type described in U.S. Pat. No. 5,577,405 (Shore et al.), a liquid lubricant is pumped from remote storage tanks for delivery to the individual roll stands, where it is applied via internal networks to the bearings, gears and other associated components housed within the roll stands. At the same time, cooling water is continuously applied externally to the work rolls and associated guides.
The majority of the internal components, e.g., drive shaft bearings, bevel and pinion gear sets, etc., are substantially isolated from the external environment, and thus the lubricant being applied to those components is not likely to become contaminated by the externally applied cooling water and any entrained dirt and mill scale.
However, certain other components are vulnerable to contamination. This is particularly true of the work side roll shaft bearings which are located directly adjacent to the work rolls, and which are separated from externally applied cooling water and entrained particulates by complicated seal assemblies. As the seal assemblies undergo normal wear, sealing integrity is compromised, resulting in contamination of the lubricant being applied to the work side shaft bearings. The lubricant applied to those particular bearings accounts for only about 10-15% of the total lubricant being supplied to each roll stand.
Conventionally, each roll stand is provided with a single outlet through which all of the lubricant supplied to that stand is drained and returned to the system storage tanks. With this arrangement, the relatively small amount of contaminated lubricant from the work side roll shaft bearings is mixed in with all of the returning lubricant, which results therefore in all of the returning lubricant being contaminated. Thus, large capacity storage tanks are required to provide adequate dwell time for contaminating particulates to settle out through gravity, and high capacity vacuum dehydrators or centrifuges are required to remove the contaminating water. By way of example, a conventional lubrication system servicing an eight stand finishing block will require two 21,000 liter storage tanks and vacuum dehydrators or centrifuges having power ratings on the order of 90 kw. Installations of this type and size are expensive and costly to operate and maintain.